[Sync] replace the flat layout with the unified stow tree

Supersedes the old flat .config/ layout (last published 2026-06-28) with the
private repo's structure: one shared base plus per-host overlays.

- packages: common/ gui/ lw/ fl/ wm/ plus install.sh and bin/ tooling
  (dotsync, reconcile-hyde.sh)
- new README covering the layout, deploy order and the HyDE dependency
- current HyDE waybar rig (layouts/, cava), pi agent extensions, claude/
  config, tmux, presenterm, aichat roles
- fish: kp (keepassxc-cli + fzf picker, db path from $KP_DB) and
  bind_M_n_history (alt+1..9 recalls the nth history entry)
- drops cruft that should never have been tracked: the duplicate top-level
  .pi/ copy, btop.log, zellij config.kdl.bak, fish_variables
- .pi/agent/auth.json is gitignored; auth.json.example ships instead

Host-specific work sessions and the personal backlog stay in the private
tree. Endpoint locators in the llamacpp/whisper guides are placeholders
($SERVER, <own-domain>) — the guides themselves stay, since they are the
useful part.

.ignore

@@ -0,0 +1,12 @@
+# Search config for THIS repo only (ripgrep / fd / telescope read .ignore).
+#
+# Everything this repo holds lives in dotfiles and dotdirs — common/.config, gui/.config,
+# common/.pi, common/.bashrc — which rg and fd skip by default, so an unqualified search
+# here returned nothing at all. Un-hide them, then put back the two dirs that would swamp
+# every result: negating .* alone drags in the whole of .git, and .claude/worktrees holds
+# entire checkouts of this same repo (background sessions create them), so every hit would
+# appear several times over. Scoped to this directory tree; searches elsewhere on the
+# machine are unaffected.
+!.*
+.git/
+.claude/